Lung cancers are common and most often present with metastatic disease that cannot be cured by systemic therapies. Recent non-small cell lung cancer (NSCLC) trials of tyrosine kinase inhibitors (TKI) targeting the epidermal growth factor receptor (EGFR) demonstrated partial responses in the majority of patients with activating EGFR mutations, but complete responses are rare and median progression-free survival remained below a year. In NSCLC patients without EGFR mutations, EGFR TKIs produce objective responses in less than 10% of patients, but with a small, statistically significant prolongation of survival. The development of drug resistance and progressive disease is universal. Improved therapy is clearly needed in both groups. Advanced lung cancers possess inherent or acquired survival mechanisms that can protect the cells from EGFR inhibition. Thus, the discovery of pathways that mediate these compensatory survival mechanisms could reveal novel therapeutic targets that would render kinase inhibition a more effective therapy for lung cancer. In the last grant period, we used a genome-wide shRNA screen and gene expression profiling to identify genes that when inhibited sensitize EGFR mutant and EGFR wild-type NSCLC cells to EGFR inhibition. These studies identified the FGFR and Wnt/-catenin pathways as mechanisms of resistance to EGFR TKIs. We further showed that genetic and pharmacological inhibition of the FGFR pathway and multiple components of the canonical Wnt/-catenin pathway identified in this screen, including tankyrase and casein kinase 2 (CK2), potentiated EGFR inhibitor therapy in vitro and in vivo. In this project, we propose to identify, validate and characterize signaling mechanisms underlying the inability of EGFR TKI to elicit complete therapeutic responses, in order to develop novel therapeutic combinations that can improve outcomes for patients with NSCLC. Importantly, we have been successful in the past in translating discoveries into biomarker-driven clinical trials. We will achieve these goals through three aims: 1) Pre-clinically and clinically evaluate the roles for FGFRs in innate resistance to EGFR TKI including the development of biomarkers and conduct of a Phase 1/1b clinical trials, 2) Determine optimal biomarkers for and the clinical efficacy in a Phase I/Ib clinical trial of combining EGFR TKI with tankyrase inhibitors for treatment of NSCLC, and 3) Determine biomarkers and establish the pre-clinical efficacy of combining EGFR TKI with CK2 inhibitors for treatment of NSCLC. By targeting multiple pathways, the ultimate goal of these studies is the development of therapeutic strategies for NSCLC patients that minimize the development of drug resistance and improve therapeutic outcomes.